Snowflake is definitely one of the better brands of shavings out there. I've used it myself with no issues. If your hammie isn't scratching, excessively sneezing or losing fur then you don't need to be worrying about allergens.
At the hamsters shows, we are required to have all hams (with the exception of long haired Syrians) on Woodshavings in their show pens so if they were anything to be majorly worried about, I don't think it would be a requirement in showing
